JPH0868817A - Method and device for measuring c/i ratio of same or neighboring channel-interference signal with digital-type movable radio system - Google Patents

Abstract

PURPOSE: To measure the C/I ratio of the same or each other neighboring channel interference waves by envelope-demodulating a signal received from a receiving antenna with a measurement receiver to digitalize scanned values for an envelope. CONSTITUTION: A signal received by a receiving antenna 1 at a receiving point is envelope-demodulated with a measurement receiver 2 and scanned at preset time intervals in a limited measurement time period with an A/D converter 3, and N-pairs of scanned values for an envelop are digitalized and memorized as 1-N continuous sequences of square values for the envelop in a computer 4. Two types of subsidiary variables are calculated from the memorized values to estimate a C/I radio in proper steps. In this way, the measured value for the C/I ratio is estimated as the function of a time from measured receiving output instead of costly collation measurement and from the analyzing calculation of the C/I ratio by using a time function value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a digital mobile radio system using phase modulation of high frequency carrier oscillation within a transmission band, and directly measures the ratio of information signals to unnecessary signals. . Therefore, the method of the present invention is
It can be advantageously used in a digital mobile radio system based on the M standard. In that case, the C / I ratio is the ratio of the reception output of the desired information signal C (carrier wave) to the unwanted interference signal I (interference wave) at the reception position.

[0002]

2. Description of the Related Art Conventionally, a method capable of directly measuring a C / I ratio in a digital mobile radio system is known. In this case, directly and without decoding the information contained in the transmission, only by the measurement-technical detection of high-frequency values and their processing, ie the evaluation of the received power, C
Means to perform a / I ratio measurement. Previously, GS
In the M mobile radio system, first, the reception output RXL for the receiver
It is known to determine the relationship between EV and bit error rate RXQUAL in the form of calibration measurements in the absence of co-channel interference and in the case of limited co-channel interference. In this way, the measurement point of the relation of C / I = f (RXLEV; RXQUAL) was obtained by the laboratory measurement which is expensive. In such an empirical method, the calibrated receiver is used for the C / I in the field measurement.
It can be used for measurement. In a simple expression, the "poor" C / I ratio (that is, the presence of an interference wave) is confirmed by the "poor" reception performance, that is, the high bit error rate, simultaneously with the high reception power. In addition, C / I for co-channel interference in an analog mobile radio system using frequency modulation of high frequency carrier oscillation
Methods for measuring the ratio are known. Such a method is described in IEEE Bulletin VT38 Vol.
It is described in pages 7 to 13 of February 2007.

[0003] The methods that have been used up to now do not allow the simultaneous use of high power at the same time due to the presence of co-channel interference, only if it can be denied that there is a reason other than co-channel interference that degrades the performance during measurement. There is a serious drawback that the conclusion of "poor" reception performance is correct. However, for this purpose, the parameters such as speed and fading profile, which are the basis, must be known at the time of measurement, and thus the above cannot be guaranteed exactly. In addition, for RXQUAL and RXLEV measurements, GSM Recommendation 05.0 is not negligible for the desired measurements.
There is a drawback described in item 8. The methods used so far are, first of all, as described above, C / I = f (RXLEV;
Since a huge amount of measurement tests in a laboratory must be performed in advance in order to obtain the RXQUAL relationship, the cost is extremely high.

[0004]

It is an object of the invention to develop a method for measuring the C / I ratio in co-channel as well as adjacent channel interference, which is considerably simpler and more compelling than known methods. To do. In that case, costly calibration measurements that were normally performed until now would be discarded. Furthermore, no interference with the mains supply should be made. Typical characteristics of GSM mobile radio systems, such as the TDMA time frame structure, must be properly included in this new method.

[0005]

The method of the invention is premised on phase modulation of the high frequency carrier oscillation in the transmission band. The signal received by the receiving antenna 1 at the receiving position is subjected to envelope demodulation in the first operation step. The envelope-demodulated signal is then scanned and digitized at predetermined time intervals ΔT for a limited measurement time Tges. As a result, with the time interval ΔT between the measurement times Tges, the envelope R
Scanning values of the N pairs of (t) is the _i = 1-N t i and t _i +
It is digitized at the time of ΔT, and the square of the envelope R ² (t)
Are stored as a continuous sequence of 1-N. The auxiliary variables X ′ and Y ′ are calculated from the values stored as the 1-N sequence of the squared R ² (t) of the envelope. The calculation of the auxiliary variable X ′ is calculated at the time points ti and ti + ΔT during the measurement time Tges, and the 1-N pairs of the envelope R (t) are digitized as a continuous sequence of i = 1-N. It is based on the scan value. At time t i (i = 1−N), the N R (t) values are subsequently squared, the individual squares of 1−N are summed, and the sum is divided by the number N. The result of this calculation is represented by X '. The auxiliary variable X ′ is proportional to the average sum power of the information signal s (t) and the disturbing signal i (t), which are single signals sent to the receiver input during the measuring time Tges. The second auxiliary variable Y'is also calculated from the digitized scan value of the envelope R (t). First, the difference of N between the scanning values of the envelopes that are squared and are continuous at time intervals ΔT is calculated. This difference is squared and summed. Sum of squared differences N
Is divided by N. Numerical value Y'calculated in this way
Is proportional to the quadruplet product of the single outputs of the signal s (t) and the signal i (t) if the total measurement time Tges and the time difference ΔT are properly selected. The auxiliary variable Y'is modified using the modification coefficient (k) before the next processing. The correction coefficient k includes the value of ΔT and an error value that is a typical value for the phase modulation method adopted.

The measuring device necessary for carrying out the method of the invention comprises a measuring receiver for envelope demodulation, which is connected to the receiving antenna 1 at the receiving position. Measuring receiver 2
The output signal is sent to the analog / digital converter 3 connected after the measuring receiver 2 for the next processing. This analog-to-digital converter scans the output signal of the measuring receiver at time intervals ΔT and sends it to a computer 4 connected after the analog-to-digital converter 3 by quantization in the next process.

[0007]

EXAMPLES The present invention will now be described in detail based on examples. The C / I measuring method of the present invention is premised on the phase modulation of the high frequency carrier oscillation in the transmission band. In the block diagram of the apparatus of the present invention shown in FIG. 1, block 1 shows a receiving antenna at a receiving position. Block 2 represents the measuring receiver used for envelope demodulating the signal sent from the receiving antenna. The output signal of the measuring receiver 2 is sent to an analog / digital converter 3 connected after the measuring receiver 2 for further processing. This analog / digital converter scans the output signal of the measuring receiver 2 with a time interval of ΔT during the measuring time Tges, and is connected after the analog / digital converter 3 by the quantization by the following processing. The computer 4 is accessed.
This can also be achieved using a personal computer. In that case, the analog / digital converter 3 is composed of a commercially available insertion card built in a personal computer and capable of a maximum scanning frequency of up to 200 kHz. The maximum scanning frequency of 200 kHz is 5 μs,
Corresponds to the minimum time ΔT between two adjacent scan points.

The rationale for the method according to the invention will now be described in detail. The signal of the desired carrier wave (information signal C) received by the receiving antenna 1 is

[0009]

S (t) = S (t) sin [2πf ₀ t + φ (t)] (1), where φ (t) contains the information to be transmitted, and in particular GSM For modulation used in mobile radio systems,

[0010]

[Equation 2] Can be expressed as In equation (2), g (r) represents the transmission fundamental pulse (Gaussian pulse), and h is GMS.
In the case of K, it has a value of 0.5 (modulation index), i represents the symbol index and a _i ε (+1, -1) is the symbol to be transmitted. Due to the effects of fading, the amplitude of the received signal depends on time, which is represented by s (t). Next, only theoretically consider the case of more severe co-channel interference. But this new method
It is equally applicable to adjacent channel interference. The following equations apply to co-channel interfering signals at the receiving location.

[0011]

I (t) = I (t) sin (2πf ₀ t + α (t) + φ ₀ (3) where φ ₀ is the zero phase angle.
The amplitude is time-dependent due to the effects of fading represented by (t). The following equations apply to the sum signal of s (t) and i (t).

[0012]

[Equation 4] Is. next,

[0013]

## EQU00005 ## Consider the square of the envelope that gives R ² (t) = S ² (t) + I ² (t) + 2S (t) I (t) cos φ (t) (6). Based on equation (6), the square of the envelope is

[0014]

(Equation 6) Due to the addend S ² (t) + I ² (t) that fluctuates with and the frequency modulation due to the phase modulation of the information and interference signals,

[0015]

## EQU00007 ## This includes the addend 2S (t) I (t) cos .phi. (T) which varies with d / dt [.phi. (T)] >> fs (8). According to equation (8), the term S ² (t) + I ² (t) and the term 2S (t) I (t) cos φ (t) can be separated, and C
/ I measurement can be performed. The C / I measurement is performed based on the method described below. In that case, it is assumed that φ (t) is evenly distributed at intervals [0.2π]. The following is a brief description.

[0016]

[Equation 8] Here, the upper line means the calculation of temporary average value calculation. Solving equations (9) and (10) gives the C / I ratio to be measured.

[0017]

[Equation 9] In terms of measurement technology, the following sum is calculated by digitization and reprocessing using a personal computer.

[0018]

[Equation 10] Further, if the square of the envelope generated in the case of t _i + ΔT is further included, the following is obtained.

[0019]

[Equation 11] Is.

[0020]

[Outer 1] To be selected. If these conditions are met, Y '=
Since Y and X ′ = X, based on Equation 11, C
/ I measurement can be performed. According to the experiment, ΔT ≦ 1
In the case of 00 μs, the conditions S (t) to S (t + ΔT) and I (t) to I (t +) for use in the GMS system.
It has been found that ΔT) is sufficiently well met.
Furthermore, during a sufficiently long measurement time (≧ 1 second),

[0021]

[Outside 2] X is satisfied. At the same time, for measurements on signals modulated according to GMS,

[0022]

[Outside 3] It turned out not to be. However, time ΔT ≦ 100μ
For s, equation (13) becomes

[0023]

[Equation 12] Can be simplified to the expression. 2cos here
φ (t) cos φ (t + Δ

[0024]

[Outside 4] This is a typical value for the method. The value of this error term can be k in laboratory measurements. The error term k is the phase difference φ
It is a correlation between (t) and φ (t + ΔT), or a similar scale. For example, as ΔT,

[0025]

[Equation 13] The above shows that when the two phase differences between s (t) and i (t) are of infinite length to each other (ΔT → ∞), there is no correlation between them. Y'according to the error term k
Can be fixed,

[0026]

[Equation 14] And equation (11) can be used to measure the C / I ratio. A more detailed description will be given based on an example in which the C / I ratio can be measured. When measuring the C / I ratio, first, all scan values of the analog / digital converter 2 are stored in the computer 3 during a measuring time of, for example, 4 seconds. When the scanning speed is 200 KHz, this scanning value is the squared value R ² (t) of the envelope, 4 s / 200000 s.
^-1 = 800,000. First, this 1-N = 8000
With a value of 00, for X'according to equation (12),
Further, for Y ′, the sum total is calculated by the computer 4 according to the equation (13). For equation (13),
The parameter ΔT is ΔT = 5 from the time interval between adjacent scan values.
μs. After that, the above calculation results of X ′ and Y ′ are included in the equation (11) by including the correction coefficient k based on the equation (16), and the C / I ratio is calculated by the computer 4. When this calculation is finished and is preferably stored in the computer 4, for example for later reprocessing, the scan value can be recorded again and the C / I ratio calculation can continue. In a further advantageous configuration of the invention, a GPS receiver (Earth projection positioning system) 5 is connected to the computer 4 as an auxiliary. GPS in addition to C / I ratio
Since the location information supplied by the receiver is stored,
It is possible to display according to the location of the C / I ratio, which is important in use. This is because this new measuring method is implemented from a moving measuring vehicle.

[0027]

A feature of the method of the present invention is that the measured C / I ratio is not a costly calibration measurement, but rather as a function of time from the measured received power and also of the function value of this time function. It is to be calculated from the analytical calculation of the C / I ratio used. Besides, GSM like TDMA timeframe structure
The typical characteristics of mobile radio systems are properly handled by the method of the present invention. The C / I ratio is the bit error rate (RXQUA
It is not measured via an auxiliary variable, such as L), but from the direct action variable, ie from the time course of the received power, which is known from the ratio of the carrier C to the jammer I at the receiving position.
The new method then does not intervene in the mains. Another advantage of this new method is that it minimizes the hardware cost of making measurements.

[Brief description of drawings]

1 is a block diagram of a measuring device according to the present invention.

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Claims (3)

[Claims] 1. A digital mobile radio system using position-modulated high-frequency carrier wave oscillation in a transmission lane,
In a method for measuring the C / I ratio of co-channel or adjacent-channel jamming signals, the received signal entering the antenna is envelope-demodulated, after which a specific time difference ΔT is set for a limited measurement time (Tges). Envelope value R (t) is i = 1
-N, scanned at t _i and t _i + ΔT, digitized and stored as a 1-N continuous permutation of the square of the envelope R ² (t), the square of the envelope 1 of R ² (t)
The information signal s (t) sent to the receiver input during the measuring time Tges from the values stored as the sequence of -N
And a numerical value X'which is proportional to the average sum output of the single outputs of the disturbing signal i (t) is calculated, while the total measurement time (Tge
s) and the time difference (ΔT) are appropriately selected, a numerical value Y ′ that is optimally proportional to the quadruple product of the single output of the information signal s (t) and the interference signal i (t) is calculated, The calculated numerical value Y'includes the correction coefficient (k), and the information signal s
A measurement characterized in that (t) and a transition to a numerical value Y which is substantially proportional to the quadrupling product of the single output of the disturbing signal i (t) and the C / I value is subsequently calculated. Method. 2. An apparatus for measuring the C / I ratio of co-channel or adjacent-channel interference signals in a digital mobile radio system, wherein a computer is provided to a receiving antenna (1) at a receiving position via an analog / digital converter (3). A measuring device comprising a measuring receiver (2) connected to (4). 3. When measuring from a mobile measuring vehicle, the computer (4) is connected to a GPS receiver (5) which sends position information for displaying the C / I ratio according to the location to the computer (4). The measuring device according to claim 2, wherein